1. Field of the Invention
The present invention relates to a multi-mode terminal, and more particularly to a method and apparatus for determining a reconnection time point for a packet service in a multi-mode terminal which provides two distinct mobile communication schemes.
2. Description of the Related Art
Currently, mobile communication technology is evolving from the Code Division Multiple Access (CDMA) and European GSM (Global System for Mobile communication) systems, which are 2nd generation network systems, into a 3rd generation network system, such as a Wideband CDMA (WCDMA) system. Since there is a vast and well-equipped service area using the 2nd generation communication scheme, the service area using the 3rd generation communication scheme is being extended even broader while the base facility for the 2nd generation communication scheme is being utilized, during this time of transition. Therefore, a terminal designed to receive a service specified in the 3rd generation network during transition is produced as a multi-mode terminal, which can support the existing 2nd generation communication scheme in addition to the 3rd generation communication scheme.
Such multi-mode terminals include an idle handover function for performing a mode transition between a WCDMA mode and a CDMA mode in an idle state, a traffic handover function for performing a mode transition to a CDMA mode without discontinuance of communication when the terminal enters a shadow area from a WCDMA network during communication, and a packet call reconnection function for performing a mode transition to accomplish reconnection when a handover occurs in a mode of receiving a packet-type data call. These functions are economical since they utilize the existing CDMA network in the 2nd generation system, but have a disadvantage of needing complicated hardware and software of the terminal, due to the need for quick handover between different modems.
The operation of a terminal performing the packet call reconnection function will now be described with reference to FIG. 1, which illustrates an area in which general CDMA and WCDMA network systems are established. The area having the CDMA and WCDMA network systems is divided into a dedicated CDMA service area and an overlapping service area in which both CDMA and WCDMA services are supportable.
When operating in a WCDMA mode, the multi-mode terminal 10 receives an IP address, which is required for a packet service, from a WCDMA base station in a WCDMA network area (i.e., an overlapping service area 30), and is provided with a packet service (PS). Thereafter, when moving into a dedicated CDMA service area 20 through a boundary area, the multi-mode terminal 10 receives a system parameter message representing a handover instruction from a CDMA based station. When such a handover environment occurs, the packet service becomes disconnected in order to provide a corresponding service, so that the multi-mode terminal 10 performs reconnection to a packet call in order to continuously use the previous packet service. Therefore, the multi-mode terminal 10 performs reconnection for a packet service call with the CDMA base station, to which the terminal is handed over, and then ends the packet service call with a WCDMA base station.
In addition, when the multi-mode terminal 10 is located in a weak electric field area, which corresponds to an oblique-line region 40, the multi-mode terminal 10 unconditionally performs a handover operation to a target network according to an instruction issued from the target network, without determining the quality of the service provided from the target network and the currently-connected network. However, although a multi-mode terminal, which is located in an weak electric field area, receives a handover instruction, it is efficient for the multi-mode terminal not to perform a handover if the quality of the service provided from the network currently in use is superior to that provided from a handover target network.
As described above, according to the prior art, it is important to timely perform a handover when a handover request is received in a multi-mode terminal which performs packet communication using different mobile communication technologies (e.g. CDMA and WCDMA networks). However, the conventional multi-mode terminal unconditionally performs reconnection for a packet service according to handover instructions issued from a network, regardless of the quality of service.